The present invention relates to a mechanism for adjusting the spatial relationship between the bottom and the back of a chair which is particularly resistant to dislocating forces, such as would occur when the chair is in a vehicle (car, train, airplane, etc.) which is involved in a crash or other accident. The change in spatial relationship between the bottom and the back of a chair usually involves a change in the angle of reclination of the back with respect to the seat, so that the individual occupying the chair can sit up or recline, as he desires, and the invention will be here specifically disclosed in connection with such a recliner.
Conventional seat recliner mechanisms have used various devices for adjusting the spatial relationship between the seat bottom and the seat back. Such devices may be actuated manually, by manipulating a handle or rotating a knob, or they may be power driven. Seats of that character are widely used in vehicles, such as automobiles or airplanes. Such vehicles are all too frequently subjected to severe stresses, as in the case of an automobile collision or an airplane crash. While airplane crashes usually involve catastrophic damages which may well destroy the chairs is any event, most automobile collisions or crashes are not of that character, but they still subject the seats in the cars to very severe stresses. It is therefore important that the seats be able to withstand such stresses so as to minimize the cost of repairing the damage attendant upon such a collision.
Conventional seat recliner systems for the automotive industry often consist of a motor which drives a worm gear which in turn rotates a nut on a feed screw of rotates the screw in conjunction with a fixed nut. There are many drawbacks to those conventional seat recliner systems. They require load bearings for the shaft and complex housings to contain and mount those bearings, and the bearings and housings must themselves be strong enough to withstand the shock of a collision. The driving connections between motor and shaft are also subject to excessive stresses. All of this greatly increases the cost, weight and complexity of the assembly.
Some examples of linear seat reclining systems include U.S. Pat. No. 5,199,764 to Robinson, which discloses a linear, power seat recliner apparatus for controllably adjusting the angular position of a seat back relative to a seat cushion. The apparatus comprises a master recliner having an integrally mounted motor, a slave recliner mechanism, and an actuator cable connecting the slave and master recliner mechanisms for transmitting torque from the motor to the slave recliner mechanism. The motor simultaneously drives each of the recliner mechanisms. The master and slave recliner mechanisms have a threaded rod assembly interconnected to a transmission assembly for providing desired speed reduction and linear reciprocal movement of the rod.
Similarly, U.S. Pat. No. 4,962,963 to Robinson discloses a linear, power seat recliner apparatus. The actuator shown in FIG. 5 of Robinson comprises an electric motor 30 which, through a system of gears, drives a helical gear nut 112. The helical gear nut movement in turn causes linear motion of rod 32. The Robinson device requires bearings within bearing housing assembly 94, which increases weighs, cost and complexity of the device
U.S. Pat. No. 3,583,762 to W. Striem discloses a hand-operated bucket neat back recliner comprising a spindle with a hand reel and oppositely threaded ends which screw into nuts mounted by rubber pieces to absorb the angle changes as the back is adjusted. Turning the head reel adjusts the relative distance between the nuts, which are respectively connected to the seat bottom and back.
U.S. Pat. No. 5,335,965 to Sessini discloses separate appositely threaded parts 30 and 33 which are moved toward and away from one another to adjust the lumbar back support in a seat.
Examples of other seat recliner systems include Brandoli U.S. Pat. No. 4,685,734, Elleman U.S. Pat. No. 2,498,106, Rees U.S. Pat. No. 5,295,730, Bray U.S. Pat. No: 5,435,624 and Weston U.S. Pat. No. 4,402,547.
In none of these patents are dislocative stresses adequately and simply taken can of, particularly where an external power drive such as an electric motor or the like is employed. Efforts to minimize the transfer of loads to the motor puts specifically involve use of extensive and complicated beatings and bearing housings. There is thus a need for an economical design for a linear power seat recliner system which is capable of withstanding severe mechanical stresses.
It is a prime object of the present invention to devise a seat recliner system which at minimum cost is capable of withstanding maximum and disocative force.
It is a further prime object of the present invention to devise a power seat recliner system in which the operational loads and the loads produced by collision or the like is neither transmitted to the motor which drives the system nor to costly and essentially fragile bearings and baring housings.
As a corollary to the above, it is an important object of the present invention to devise a recliner drive which, because of the strength inherent in the arrangement of the parts, enables those puts and their housing to be made of relatively inexpensive materials such as plastic or relatively inexpensive metals.
To these ends, the system of the present invention utilizes a shaft having first and second portions which an appositely threaded, with inwardly and outwardly moving elements at both ends thereof threadedly engaging those appositely threaded portions, those parts being non-rotatably received within a housing and those parts in turn being operatively connected to the chair bottom and back respectively. External means, such as a motor, is drivingly connected to the shaft so as to rotate the latter, as, for example, by a worm and gear arrangement within the housing or a driving cable connected to an end of the shaft. Forces applied to the assembly, such as those forces acting on the chair bottom and back respectively, will be taken up by the shaft structure itself and the threaded engagement between that shaft and the parts connected to the bottom and back respectively. The shaft itself is structurally strong, as is the threaded engagement, particularly if a fine thread is employed, the exerted forces are taken up by the shaft structure, since special bearings for the shaft an not required, and thus faces are not transmitted to any bearing, nor are such forces transmitted to the driving motor, thus making the structure exceedingly sturdy and exceedingly simple.
This engagement therefore has many advantages over the prior art. With the motor positioned remote from the forces exerted on the shaft either when it is operated in normal fashion or when it is subjected to serious dislocative forces, it is the shaft itself which takes up those farces, and since it is a unitary structure it can do that very efficiently. In addition, the design of the housing is greatly simplified and the use of delicate bearings is entirely eliminated. The simplified structure further eliminates the need for periodic adjustments of the mechanism. Thus improved operation is accomplished at lower cost while at the same time achieving greater safety and reliability.
To the accomplishment of the above, and to such other objects as may hereinafter appear, the present invention relates to the design of a direct load recliner device as defined in the appended claims and as described in this specification, taken together with the accompanying drawings, in which: